Transistor point contact arrangement



Dec. 4, 1956 K. LEHOVEC 2,773,224

TRANSISTOR POINT CONTACT ARRANGEMENT Filed Dec. 31, 1952 F 2 l4 I4 I 2| I3 3 I3\ 22 22 42 xx II INVENTOR. KURT LEH OVEC HIS AT TORNEYS United States Patent TRANSISTOR POINT CONTACT ARRANGEMENT Kurt Lehovec, Williamstown, Mass., assignor to Sprague Electric Company, North Adams, Mass., a corporation of Massachusetts Application December 31, 1952, Serial No. 328,948

6 Claims. (Cl. 317-235) The present invention relates to new and improved point contact constructions for transistors.

The field of transistors is now so Well known that it is not deemed necessary to devote any of the present specification to purely descriptive matter relating to this subject. In this connection, reference is made to the text Holes and electrons in semiconductors by Schockley, the entire November 1952 issue of the Proceedings of the Institute of Radio Engineers, as well as other publications.

One type of transistor which presently shows a great deal of promise requires the use of two point contacts termed the emitter and the collector bearing against a single crystal of a metal such as germanium, silicon, or

other related semiconducting materials. A third low resistance electrical connection is made to such a crystal. In order to obtain satisfactory operating characteristics with this type of construction the two point contacts must be positioned relatively close, and must remain in a comparatively fixed position.

It is now a common procedure to hold these point contacts or probes in place by the use of a small amount of tension and a stiif gel-like filler material. Other means for accomplishing the same result have been suggested. These include the use of stiff fabric-like inserts through which the probes are inserted; the use of an adjacent wall upon which the point contacts are mounted; and other means. The number of suggestions made on the subject of positioning wire probes in itself indicates the inefiectiveness of the presently used procedures.

An object of the present invention is to improve upon the aforegoing and related methods for positioning wire point contacts against a body of a semiconducting material used in a transistor. A further object is to produce new and improved transistor constructions. These and other aims of the invention, as well as the advantages of it will be apparent from the following description and claims, as well as the accompanying drawings in which:

Figure 1 diagrammatically illustrates a transistor formed in accordance with this disclosure; and

Figure 2 is a diagrammatic view of a modified construction of the invention; and

Figure 3 is a diagrammatic view of a still further modified construction. In all figures like numerals designate like parts.

In Figure 1 of the drawings a simple transistor construction is shown in which a small semiconducting wafer 11 such as, for example, a germanium crystal about x 50 x 150 mils in size is provided with two apertures 12 through which wire probes 14 project. Each of these probes 14 is insulated from the wafer 11 by an insulating sleeve 13 of polyethylene or the like, and is bent so that the point contacts 15 touch the same face of the crystal quite close to one another. Preferably a space of from 1 to 5 mils separates them. A low resistance contact 16 of known type is made to the wafer 11 through the wire 17.

The modification shown in Figure 2 of the drawing difliers from the construction of Figure 1 solely in that the adjacent point contacts 15 are positioned upon opposite sides of a wall 21 in small cavities 22 formed within the wafer 11. Preferably, this wall 21 should be from about 1 to about 5 mils thick. The construction shown in this figure has the advantage that with it the point contacts are not apt to be dislodged due to handling, as when encasing the entire unit in a protective insulating resin.

The same advantage is derived from the construction illustrated in Figure 3. Here the wire probes 14 are inserted through the holes 12 in the wafer 11 from opposite directions so that the point contacts 15 project towards one another within the cavities 342, but are separated by the Wall 31 which is preferably of the thickness previously indicated.

The various apertures and holes or cavities herein indicated can be found in a variety of methods known to the art, such as, for example, by the use of dental abrasive equipment.

The herein described invention has a number of advantages. Perhaps one of the most important of these is comparative ease with which it adapts itself to large scale production techniques. By one procedure a comparatively large fiat body of a semiconductor can be provided with the apertures, holes, and/or cavities for a large number of transistors at the same time, the appropriate connections and probes indicated can be placed in position, and then the individual transistors actually formed by cutting the larger body. If desired, the initial block can be scored or perforated so as to assist in separating the individual units. Various known steps, not specifically indicated herein, such as, for example, etching can be carried out at any convenient stage in forming the units of the invention. Also, a construction similar to that shown in Figure 1 can be formed utilizing a very thin wafer with the point contacts positioned upon opposite sides of it in the broad manner indicated.

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope hereof, it is to be understood that the invention is not limited to the specific embodiments hereof except as defined in the appended claims.

What is claimed is:

1. A transistor comprising a body of a semiconducting material, means defining at least two closely-spaced apertures through said body, wire probe means passing through said apertures, insulating means separating said wire means from said body in said apertures, point contact means formed on the tips of said probe means, said point contact means forming rectifying contacts with parts of said body about 1 to 5 mils apart.

2. A transistor as defined in claim 1 wherein said contacts are both on the same face of said body.

3. A transistor comprising a body of a semiconducting material, means defining at least two closely-spaced apertures in said body, Wire probe means passing through said apertures, insulating means separating said wire means from said body in said apertures, point contact means formed on the tips of said probe means and positioned within cavities upon the same face of said body, said point contact means forming rectifying contacts with adjacent parts of said body.

4. A transistor comprising a body of a semiconducting material, means defining at least two closely-spaced apertures in said body, wire probe means passing through said apertures, insulating means separating said wire means from said body in said apertures, point contact means formed on the tips of said probe means positioned upon opposed sides of said body, said point contact means forming rectifying contacts with adjacent parts of said body.

"5. A transistor as defined in claim 4 wherein said point contact means are positioned within cavities.

6. A transistor sub-assembly comprising a body of a semi-conducting material, means defining at least two closely spaced apertures through said body, contact 5 means passing through said apertures and contacting said body about 1*to '5 mils apart, and insulating means separating said contact means from said body in said aper tures.

References Cited in the file of this patent UNITED STATES PATENTS Rose Jan. 16, 1951 Gray Apr. 3, 1951 Kock et a1. July 17, 1951 Spenke et a1 Aug. 11, 1953 

